June 1991 Table of Contents

Features Explaining aggregate tests

Is there a publication that explains standard aggregate tests in an easily understood manner? The ASTM standards for specific gravity, abrasion resistance, sieve analysis, and similar tests are hard reading. Read more

Features Bridge Spans Lifted 80 Feet from Barge

The four-lane Jamestown-Verrazano bridge linking North Kingstown and Jamestown, Rhode Island, underwent a 2,400-ton precast bridge span lift between 1990 and 1992. The double-cell box girder used for both the high-level approach spans and the main structure varies in depth from 10 feet to close to 33 feet. The three main spans were cast in place using balanced cantilever construction, and the high level precast approach spans were lifted into place. The work was originally bid to VSL Corp., who redesigned the high-level approach plans to permit span-by-span erection with VSL equipment. The contract was later terminated and reawarded to Atkinson-Kiewit, who decided to follow the VSL redesign, which provided the option of casting pier segments of the approach spans in place. Read more

Features Forklift-Moved Forms Simplify Parking Garage Construction

A formwork system moved by forklift rather than by crane was used to build the upper ramp of a two-level, 1,250-car cast-in-place concrete parking garage in Milwaukee. Because of the large area covered by the post-tensioned, slab-and-beam ramp, the contractor had to find an efficient way to transport formwork to the jobsite. The forming system he used consisted of beam and deck forms that can be stripped, moved, and reset using only forklifts and dollies. The main element of the system is a 60-foot-long steel beam form that rests on 18-kp support frames having hinged, height-adjustable legs. Because the beam and its framework support the deck panels, shoring is usually unnecessary. Read more

Features Why You Need a Computer -- and How to Develop a Successful System

Computers are becoming necessary pieces of equipment in the contracting business because they can enhance speed, quality, appearance, and efficiency. Computer-generated documents convey much more attention to detail and professionalism than do bids scribbled on the back of an envelope. Read more

Features Software Solutions for Concrete Pumping Companies

The small size of the concrete pumping industry hasn't justified much software development. But two specialized software packages are available. The industry standard software runs on any IBM-compatible computer and is composed of modules - disks containing instructions for the computer to perform additional tasks. The core module is Billing, Accounts Receivable, and Sales Analysis. Optional modules include Accounts Payable, Maintenance, System Tracker, and Preliminary Generation. This modular approach gives customers the flexibility to buy only what they need. The core module helps you invoice customers and collect debts. The sales analysis part of the core module allows companies to assess their top-line performance. Read more

Features Rehabilitating Ohio State's Stadium

The Ohio State University football stadium was last repaired extensively in 1948, leaving unsightly dark, irregular patches. Numerous stains, spalling concrete, and exposed steel reinforcement called for further repair of the concrete facing. Most of the precast cornices and all the precast window grilles were in an advanced state of deterioration due to freeze-thaw damage with many pieces already having fallen to the ground. Cored samples of the concrete surface in several locations indicated a depth of carbonation in the concrete ranging from one-eighth to one and one-half inches. Orange streaks also stained the exterior of the stadium concrete. Read more

Features Thin-Shell Concrete Dome Built Economically with Rotating Forming and Shoring System

The thin-shell concrete dome topping the Sundome in Yakima, Washington, has 24 wedge-shaped segments arranged in a radial pattern like the pieces of a pie. But only six wood forms were needed to cast the 24 segments because of an innovative rotating forming and shoring system. The Sundome roof has a rise of 40 feet and a maximum clear height above the floor of 80 feet. Its 24 identical wedge-shaped segments arch to a compression ring at the crown of the roof and their bases are stabilized by a post-tensioned concrete tension ring supported on 24 reinforced concrete columns. Each segment is doubly curved like a saddle to increase the stability of the dome. Read more

Features OSHA Increases Penalties Sevenfold

With its enactment of the Budget Reconciliation Act on September 5, 1990, Congress has increased maximum Occupational Safety and Health Administration (OSHA) penalties a whopping sevenfold. The maximum penalty for a willful or repeated violation is now 70,000 dollars, up from 10,000 dollars, and the maximum penalty for a serious or other-than-serious violation is 7,000 dollars, up from 1,000 dollars. These amounts are ceilings, not floors. But to ensure that flagrant violators are fined sufficiently, the minimum penalty for a willful violation is now 5,000 dollars. Read more

Features Customize Every Batch with Computers

Using fixed weights of variable ingredients under variable conditions yields a predictable result - a variable product. To avoid problems caused by keeping ingredient weights constant, concrete should be produced to meet performance requirements in accordance with a design formula for the composite mixture. This can be done by applying computer technology. A software system scheduled for release in 1991 allows the producer to store a mixture design formula instead of batch weights in the plant control computer. The mixture design formula is supported by ingredient properties, construction needs, concrete mix performance history, and weather conditions and delivery times. Changes in information within these databases would trigger a mix proportion change. Read more

Features Making Concrete Waterscapes

Contractor Ken Macaire, based in Los Angeles and Sherman Oaks, California, uses custom carving to create regionally accurate concrete waterscapes for residential and commercial use. Santa Barbara developer John Lucian said a water feature adds one-third more to the property value. There are two ways to make permanent rock formations: use a standard mold or design each product individually. Using a standard mold is easy, but limited in design. Customized sites are structurally more durable. Read more

Features Nomograph Allows Quick Estimates of Concrete Volume for Slabs

The February 1989 issue of "Concrete Construction" contained a nomograph for use in estimating the volume of concrete needed for slabs of varying thickness and area. Joseph Deigh, a retired civil engineer, devised the nomograph so contractors could quickly determine concrete volumes on the job without having to use complicated formulas. Now Deigh has a revised version of the nomograph that works for metric and English units of measure. Both units of measure are shown side-by-side on each of the three nomograph scales. Read more

Problem Clinic Adding Water to Concrete at the Jobsite

What do ACI and ASTM standards say about adding water to ready mixed concrete at the jobsite? Is it permitted? If so, when and how should it be added? Read more

Close X